When the label is unreadable
Enter diameter and height in millimetres to find candidates. Measurements never establish equivalence by themselves.
Candidates within ±0.2 mm
Measurements produce candidates, never an automatic equivalence verdict.
Measure the widest diameter and total height in millimetres with a suitable calliper. Enter positive decimal values. The finder uses a conservative ±0.2 mm window to allow for ordinary measurement variation; it does not round every nearby commercial size into one result.
LR44, SR44W, SR44SW and PR44 can share an 11.6 × 5.4 mm envelope while using alkaline, silver-oxide or zinc-air chemistry and different operating behaviour. Conversely, CR2032 and CR2025 share a 20 mm diameter but differ by 0.7 mm in height. Dimensions narrow the search; the complete code and electrical requirements decide the family.
Open each candidate record and check its cited dimensions, chemistry, nominal voltage and drain designation against the device instructions. Never stack cells or alter a compartment to compensate for height. See How to measure a button battery and Why the same size does not mean equivalent.
Several silver-oxide watch cells are 1.65 mm high but have very different diameters. Compare SR416SW / 337 at 4.8 × 1.65 mm, SR716SW / 315 at 7.9 × 1.65 mm and SR1116SW / 366 at 11.6 × 1.65 mm. A matching height cannot compensate for the wrong diameter.
After narrowing the list, read Battery voltage and chemistry before treating any candidate as a substitute.